Need full information about sending datas to mysql using database relations in Spring boot

Question

I am new to Spring boot and planning to build School managemanet application using Spring boot and Mysql.However, im on stuck while sending student data to his category.There is seperate table called "Faculty" and Im going to Send data from table "Student". The problem is in the form there is "Select option" to send data for the specific faculty. However, the unknown error is being displayed that I dont understant why? I would be grateful if you send me full information regarding the sending data to category using select option in form. Below what I have tried:

StudentController.class


package io.adu.Controllers;

  import java.lang.reflect.Method; import java.util.Arrays; import
  java.util.List;

import javax.validation.Valid;

import org.springframework.beans.factory.annotation.Autowired; import
  org.springframework.stereotype.Controller; import
  org.springframework.ui.Model;
import org.springframework.ui.ModelMap;
import org.springframework.validation.BindingResult;
import
  org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import
  org.springframework.web.bind.annotation.PathVariable; import
  org.springframework.web.bind.annotation.PostMapping; import
  org.springframework.web.bind.annotation.RequestBody; import
 org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import io.adu.DAO.Faculty; 
  import io.adu.DAO.Student;
import io.adu.DAO.User;
import io.adu.Repository.FacultyRepository; 
  import  io.adu.Repository.StudentRepository; 
  import io.adu.Service.StudentService;

  @Controller 
  public class StudentController {

  @Autowired 
  StudentService service;

  @Autowired 
  FacultyRepository repository;
  @Autowired
 StudentRepository studentRepository;    

  @GetMapping("/addStudent")
  public String viewStudentsList(Model model) {
      List<Student>students = studentRepository.findAll();
      List<Faculty>faculties = repository.findAll();
      model.addAttribute("addstudent",true);
      model.addAttribute("students",students);
      model.addAttribute("faculties",faculties);
      return "addStudent";

  }

  @PostMapping("/addStudent")
  public String showStudents(@Valid @ModelAttribute("addStudent")Student student,BindingResult result,ModelMap model){
      Student student = new Student();
      List<Faculty>faculties = repository.findAll();

      model.addAttribute("Student",student);
        model.addAttribute("faculty",new faculty());
          model.addAttribute("addstudent",true);
         service.addStudent(student);
      return "addStudent";
  }





 StudentEntity.class

    @Entity
    @Table(name="student")
    public class Student implements Serializable {

        private static final long serialVersionUID = 1L;

        @Id
        @Column(name="student_id")
        private int id;
        @Column(name="student_name")
        private String name;
        @Column(name="student_email")
        private String email;
        //@Column(name="student_name")
        //private String faculty;
        @Column(name="paid_amount")
        private String paidamount;


        @GeneratedValue(strategy=GenerationType.IDENTITY)


         @ManyToOne
            @JoinTable(name = "faculty_students",
                        joinColumns =  @JoinColumn(name = "student_id"),
                        inverseJoinColumns = @JoinColumn(name = "faculty_id"))
        private Faculty faculty;

        public int getId() {
            return id;
        }
        public void setId(int id) {
            this.id = id;
        }
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
        public String getEmail() {
            return email;
        }
        public void setEmail(String email) {
            this.email = email;
        }
        public String getFaculty() {
            return faculty;
        }
        public void setFaculty(String faculty) {
            this.faculty = faculty;
        }
        public String getPaidamount() {
            return paidamount;
        }
        public void setPaidamount(String paidamount) {
            this.paidamount = paidamount;
        }




    }

StudentForm.html

 <form th:action="@{/addStudent}"  th:Object="${addStudent}" method="post">
                                <div class="card-body card-block">
                                    <div class="form-group">
                                        <label for="company" class=" form-control-label">Ismi</label>
                                        <input type="text" id="company" placeholder="Talaba ismini kiriting" class="form-control">
                                    </div>
                                    <div class="form-group">
                                        <label for="vat" class=" form-control-label">To'langan summa</label>
                                        <input type="text" id="vat" class="form-control">
                                    </div>
                                    <div class="form-group">
                                        <label for="street" class=" form-control-label">fakulteti</label>
                                    <select class="form-control"  th:field="${addStudent.faculties}" th:disabled="${disableFields}">
            <option th:each="faculty :${faculties}" th:value="${faculty.facultyId}" th:text="${faculty.FacultyName}">
            </option>
            </select>
                                    </div>
                                    <div class="row form-group">
                                        <div class="col-8">
                                            <div class="form-group">
                                                <label for="city" class=" form-control-label">Elektron pochtasi</label>
                                                <input type="text"  class="form-control">
                                            </div>
                                        </div>
                                        <div class="col-8">
                                            <div class="form-group">
                                                <label for="postal-code" class=" form-control-label">Status</label>
                                                <input type="text" placeholder="Budjed-Kontrakt" class="form-control">
                                            </div>
                                        </div>
                                    </div>
                                    <div class="form-group">
                                        <label for="country" class=" form-control-label">Tugilgan Sana</label>
                                        <input type="text" id="country" class="form-control">
                                    </div>
                                        <button type="submit" class="btn btn-primary btn-sm">
                                        <i class="fa fa-dot-circle-o"></i> Submit
                                    </button>

                                </div> </form>

Log Error

Caused by: org.thymeleaf.exceptions.TemplateProcessingException: Error during execution of processor 'org.thymeleaf.spring5.processor.SpringSelectFieldTagProcessor' (template: "addStudent" - line 299, col 71)
    at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:117) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.processor.element.AbstractElementTagProcessor.process(AbstractElementTagProcessor.java:95) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.util.ProcessorConfigurationUtils$ElementTagProcessorWrapper.process(ProcessorConfigurationUtils.java:633) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.engine.ProcessorTemplateHandler.handleOpenElement(ProcessorTemplateHandler.java:1314) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.engine.TemplateHandlerAdapterMarkupHandler.handleOpenElementEnd(TemplateHandlerAdapterMarkupHandler.java:304) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler$InlineMarkupAdapterPreProcessorHandler.handleOpenElementEnd(InlinedOutputExpressionMarkupHandler.java:278) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.standard.inline.OutputExpressionInlinePreProcessorHandler.handleOpenElementEnd(OutputExpressionInlinePreProcessorHandler.java:186) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.templateparser.markup.InlinedOutputExpressionMarkupHandler.handleOpenElementEnd(InlinedOutputExpressionMarkupHandler.java:124) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.attoparser.HtmlElement.handleOpenElementEnd(HtmlElement.java:109) ~[attoparser-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.attoparser.HtmlMarkupHandler.handleOpenElementEnd(HtmlMarkupHandler.java:297) ~[attoparser-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.attoparser.MarkupEventProcessorHandler.handleOpenElementEnd(MarkupEventProcessorHandler.java:402) ~[attoparser-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.attoparser.ParsingElementMarkupUtil.parseOpenElement(ParsingElementMarkupUtil.java:159) ~[attoparser-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.attoparser.MarkupParser.parseBuffer(MarkupParser.java:710) ~[attoparser-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    at org.attoparser.MarkupParser.parseDocument(MarkupParser.java:301) ~[attoparser-2.0.5.RELEASE.jar:2.0.5.RELEASE]
    ... 85 common frames omitted
Caused by: java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'addStudent' available as request attribute
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:153) ~[spring-webmvc-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.web.servlet.support.RequestContext.getBindStatus(RequestContext.java:903) ~[spring-webmvc-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.thymeleaf.spring5.context.webmvc.SpringWebMvcThymeleafRequestContext.getBindStatus(SpringWebMvcThymeleafRequestContext.java:227) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatusFromParsedExpression(FieldUtils.java:306) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatus(FieldUtils.java:258) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatus(FieldUtils.java:227) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.processor.AbstractSpringFieldTagProcessor.doProcess(AbstractSpringFieldTagProcessor.java:174) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:74) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    ... 98 common frames omitted

2020-02-03 21:02:59.704 ERROR 13336 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[/].[dispatcherServlet]    : Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.thymeleaf.exceptions.TemplateInputException: An error happened during template parsing (template: "class path resource [templates/addStudent.html]")] with root cause

java.lang.IllegalStateException: Neither BindingResult nor plain target object for bean name 'addStudent' available as request attribute
    at org.springframework.web.servlet.support.BindStatus.<init>(BindStatus.java:153) ~[spring-webmvc-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.web.servlet.support.RequestContext.getBindStatus(RequestContext.java:903) ~[spring-webmvc-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.thymeleaf.spring5.context.webmvc.SpringWebMvcThymeleafRequestContext.getBindStatus(SpringWebMvcThymeleafRequestContext.java:227) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatusFromParsedExpression(FieldUtils.java:306) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatus(FieldUtils.java:258) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.util.FieldUtils.getBindStatus(FieldUtils.java:227) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.spring5.processor.AbstractSpringFieldTagProcessor.doProcess(AbstractSpringFieldTagProcessor.java:174) ~[thymeleaf-spring5-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.processor.element.AbstractAttributeTagProcessor.doProcess(AbstractAttributeTagProcessor.java:74) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.processor.element.AbstractElementTagProcessor.process(AbstractElementTagProcessor.java:95) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.util.ProcessorConfigurationUtils$ElementTagProcessorWrapper.process(ProcessorConfigurationUtils.java:633) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.engine.ProcessorTemplateHandler.handleOpenElement(ProcessorTemplateHandler.java:1314) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]
    at org.thymeleaf.engine.TemplateHandlerAdapterMarkupHandler.handleOpenElementEnd(TemplateHandlerAdapterMarkupHandler.java:304) ~[thymeleaf-3.0.11.RELEASE.jar:3.0.11.RELEASE]

Answer 1

Please add appropriate log output to such cases as there is not enough info to help you otherwise imho (And the Service class is missing as well).

One thing I can see and propose:

• ManyToOne or OneToMany associations usually don't need a join table, unless you specifically want one. I'd get rid of that, depending on your other use-cases of faculty. A majority of use-cases where things go wrong that I see are with misunderstanding on how Hibernate's relations work.